29 



long. Owing, however, to the smalluess of the plots, it 

 is undesirable to remove samples frequently; and 

 whether or not any be taken intermediately, they 

 should certainly be taken to some depth, whenever it 

 may be decided to terminate the experiment. 



IV. EXPERIMENTS ON THE CONTINUOUS GROWTH OF 

 ROOT-CROPS, IN BARNFIELD COMMON TURNIPS, 

 SWEDISH TURNIPS, SUGAR BEET, AND MANGEL 

 WURZEL. 



1. The Field Results, and tJic Composition of the Crops. 



These experiments were commenced in 1843, and are 

 still in progress; so that this season, 1891, will be the 

 49th of their continuance. There was, however, a break 

 after the first 10 years, when, for 3 years in succession, 

 barley was grown, without any manure, over all the 

 plots, in order as far as possible to equalize their con- 

 dition, due to the previous various manuring, with a 

 view to a more systematic arrangement. Thus, the 

 different crops have already been grown as follows : 



Norfolk White Turnips . . 6 years 1843-48 



Swedish Turnips . . 4 years 1849-52 



(Barley without manure) . . 3 years 1853-55 



Swedish Turnips .. .. 15 years 1856-70 



Sugar-beet . . . . . . 5 years 1871-75 



Mangel Wurzel .. .. 15 years 1876-90 



Since the re-arrangement in 1856, there have been 

 about 40 plots, without manure or with different 

 manures. The roots and leaves are always weighed. 

 A sample of the roots is taken from each plot, and of 

 the leaves from a selection of plots. The dry matter 

 and ash are always determined, and partially dried 

 samples preserved for determinations of nitrogen, &c. 

 In each of the 5 years of sugar-beet, the sugar was also 

 determined by polariscope, in 2 of the years in the 

 produce of 40 plots, in 1 year in that of 35 plots, and 



